Effect of microencapsulation on functional and technological features of probiotic and starter cultures

Abstract

Microencapsulation is currently described as the technique that permits the physical containment into functional matrices of several categories of compounds that can benefit from this procedure. Vitamins, polyphenols, bacteriocins, living cells and other many sensitive compounds can be efficiently protected, delivered, released and easier handled when in microencapsulated form during their utilization and storage. Microencapsulation of living cells has gradually become an important area of intense research and industrial development within the wider field of microencapsulation. First applications of encapsulated microorganisms in the food sector were mainly confined to fermentation processes in which a higher recovery of enzymes, ethanol, lactic acid or antimicrobial peptides alongside a higher cell density were obtained with the use of encapsulated microorganisms. More recently, the encapsulation of probiotic bacteria has gained a great attention because of the undoubted potentiality of this technology to provide protection toward probiotics by enhancing their capability to cope with different stress factors. Probiotics are defined as live microorganisms able to confer health benefits to the host when administered in adequate amounts and, in order for probiotics to preserve their expected health-promoting effects, they need to survive during passage through the gastrointestinal tract. Accordingly, the most investigated area in the field of probiotic encapsulation is the one dealing with the development of microcapsule systems able to protect bacteria against gastrointestinal barriers and to efficiently mediate their delivery to the intestine, their target site of action. Furthermore, because probiotics are becoming an important resource for the maintenance and restoration of the normal intestinal microbiota, and in general for the human wellbeing, a great attention is currently given to the extension of the categories of foods carrying probiotics. At this regard, microencapsulation is also regarded as a valid strategy for the improvement of probiotic viability against technological and food-related hurdles in order to i) increase their survival during the manufacturing and the storage of foods and iii) to contribute to the development of innovative probiotic food carriers. Despite the relevant improvements toward the useful application of microencapsulation technology to probiotic microorganisms, some challenges still exist and need to be addressed to enable wider industrial acceptance of cell microcapsules in various production processes. Typical examples are the development of easy to use, stable and cheap microcapsules suitable for food applications, the monitoring of cell stability along the entire food production including a real storage period and the assessment of the effect of new micro-environment created within the capsules on cell metabolism. This PhD thesis deals with this context.